Make the "move" button move the banner, not the window

[BudgieInWA]

With #22, the "move overlay" button is no longer needed to work around #2. It should be transformed into a "move banner" button, simply changing the offset at which the banner is drawn, instead of moving the window. Alternatively, it is not useful enough and should be removed.

[eoakley]

I'm not confident enough that the card infos display are working flawlessly. We can do this soon.